This application requests a further 5 years of support for an Institutional National Research Service Award to support multi-disciplinary postdoctoral training in drug abuse (including nicotine and tobacco dependence) research. We request support for eight post-doctoral fellows (3-4 MD, 4-5 PhD), for primary training in one of 7 major areas: (i) systems neurobiology, (ii) molecular and cellular mechanisms, (iii) cognitive neuroscience, (iv) genetic methodology, (v) genetic epidemiology and behavioral genetic research, (vi) gene-mapping studies, or (vii) molecular genetic research on substance use disorders. In addition to specialization in a primary discipline, trainees will be encouraged to obtain a sufficient familiarity with at least one other focus area to facilitate fruitful cross-disciplinary collaborations in their research careers. The training program will ordinarily be of 3 years duration, reflecting the diverse background of our applicant pool (e.g. psychology, psychiatry, endocrinology, mathematics, economics, anthropology, sociology, neuroscience), or 2 years for those with pertinent research experience. 1-2-year post-doctoral fellowships are also offered for experienced drug abuse researchers seeking training in a new area of drug abuse research (e.g. human genetics). Thus on average 3 new trainees will be recruited each year (4 in years 11, 14). The training program will emphasize a research apprenticeship model, combining research under the mentorship of one or more experienced research mentors with more formal training through didactic courses or individualized tutorials. Major strengths of the program are the availability of a large multi-disciplinary faculty with an active program of research on substance use disorders, representing expertise in many aspects of statistical/quantitative, molecular and genetic epidemiologic and neuroscience research on substance use disorders; the highly productive research environment (with preceptors having a total of 60 relevant funded research projects, career awards and science cores); the availability of major genetic epidemiologic data-bases, and access to a large number of ongoing projects, that offer many research options to trainees; the program's location in one of the nation's leading medical schools, allowing trainees to take advantage of a rich array of didactic courses and seminars and research experiences; and the long tradition at Washington University of successful mentoring and research training of scientists and physician scientists from diverse intellectual backgrounds for research on substance use disorders.